Hull



June 28 1932. L, GH|RARD| 1,864,997

HULL

Filed Feb'. 3, 1928 g-wwnto'l,

Lu/G/ H/RARO/ W Patentecl June 28, 1932 LUIGI GHIRARDI, or' GEuoA, ITALY 12mmv Application filed. February 3, 1928. Serial No. 251,703.

The present invention relates to the hulls of ships, boats or other like craft, the object of the invention being to provide a design whereby resistance to motion is reduced to a minimum and thus high spee'ds can be obtained with economy in the propulsion expenses.

According to the inv'ention the water-line plan of the hull extends from the stem to the stern and the maximum beam dimension is above the water-line, whilst the maximum beam section is situated pronouncedly nearer the bow than the stern and the shell tapers from this point towards the stern wh'ereby the midship and the centre of gravity line are, as compared with anormal hull, much nearer the bow.

Hulls have previously been proposed, in which the water-line plan extends from the stem to the stern, whilst the maximum beam section is situated nearer the bow than the stern and the shell tapers towards the stern. Here, however, the maximum beam dimensi on is below the water-line. Hulls have also been proposed with a tapering submerged part, but here the keel takes an upward curvature towards the front of the hull so that the stem is completely out of the water and the waterline plan therefore does not eXtend from stem to stern. F urthermore in this proposal the sides of the shell eXtend parallel over .the greater part of the length. Again` hulls have been proposed in which the Water-line plan cxtends substantially from the stern to the stem. In this case however the maximum beam section is nearer the stern than the bow and the maximumtbeam section is the same above the water-line.

The present invention is diagrammatically illustrated in the accompanying drawing in which Figure 1 is a side elevation of the hull,

Figure 2 a plan of one half of the hull, depicting plan-Sections thereof on several of the horizontal lines shown in Figure 1,

Figure 3 is a cross-section on an enlarged Scale, 'depicting the beam Sections on several of the Vertical lines O to 10 shown in Figure 1, and

Figure 4 is a diagrammatic plan illustrative of the hydrodynamic pressures and forces involved during the motion and maneuvering of the vessel.

Referring to the drawing H indicated the hull, whilest lVL indicated the water-line which as will be observed extends from the stem Sm to the stern Sa so that the whole of the keel K is submerged.

The maximum beam section, as indicated by the line 7 (Figures 1 and 3) and by the cross-section is situated much nearer the bow than the stern, being preferably larger than normally, whilst from this point the submerged portion at least of the shell tapers continuously and pronouncedly to the stern as shown more cl'early in Figure 2. By this means the mi'dship and the centre of gravity which is near to the same line 7 is much nearer the bow than in a hull of usual construction. In actual practice it is preferred that this line shall be situated at a distance from the bow of about 1/3 to 14 the total length of the hull.

The power unit for propelling the vessel is arranged as usual in the region of the centre of gravity. With a design of hull according to the present invention therefore, the power unit is comparatively near the bow, but nevertheless this arrangement does not detract from the practicability of the design O but rather leads to advantages. Owing to the nearness of the power unit to the bow it is practical to have forwardly arranged propelling means because the propeller shaft or shafts need be but comparatively short which as is well recognized in the art is very desirable, not only from the point of'view of efficiency but also because such arrangement avoids complications in maintaining align-` serious extent by eddy currents, but reduce to a minimum the currents created by the stern, the latter may be pronouncedly inclined as shown in Figure 1. Shaping the stern in this way also has the tendency to direct the water downwards towards the screws, whilst it is preferred that the cross-Sections in proximf ity to the screws shall be of lesser draft, as shown, that successive cross-Sections, thus permitting water to have full access to the screws which are also protected' against breakage by collision.

It may be thought that the advantage mentioned above would be negatived in. the case of propulsion of the vessel from the rear owing to the increased distance of the power unit from the stern. This however is not so as owing to the pronounced tapering of the hull towards the sternl it 1s possible to have real' propelling means proJecting from the sides of the hull at points comparatively near the midship section and close to the power unit whilst still maintaining the aXes of the propeller shafts substantially parallel with the longi'tudinal axis of the vessel which is necessary for eificiency. Such propelling means preferably comprises a pair of screws arrangcd one on either side of the keel (/c) The increase of the maximum beam section above the normal renders it possible to install a larger power unit without occupying' too much space longitudinally of the vessel. Furthermore this increase and this installation of the power unit gives a corresponding large forecastle deck and a larger upperbridge dech which is thus rendered eminentl v suitable for the provision of landing andv take-off gear for aircraft.

It will be observed from Figure 3 that the maximum beam dimension of the hull is above the water line IFJL. In fact the great-est dimension on any cross-section is above the water line as p'enerally indicated' in this figure. In this respect therefore the improved hull diifers from those in which the greatest beam section is below the water-line.

Owing to the provision of a pronounced and continuous taper from the centre of gravity or from the midship section to the stern, eddy currents towards the rear of the vessel are reduced to a minimum, so that the rear screws work in water which is practically undis turbed or at any rate is fiowing only from front to rear and therefore these screws work with increased efiiciency in propelling the vessel. Furthermore the sides of the hull as shown in Figure 3 are made somewhat concave giving an additional tendency to direct the water downwards not only towards the rear screws but also towards the front screws.

Prcferably the upper decks which are indicated at 16 are given substanti'ally the same shape in plan as the water-line plan of the hull as shown in Figure thus reducing to a minimum the retarding action' of the air above the water-line when the vessel is in motion.

The forward situation and comparatively wide construction of the mids'hip section coupled with the rearward tapering of the hull gives rise to hydrodynamic forces which also ill'ustrate: the eficiencyvv of the construction. These: forcesI are` depict'edf inl Figurev 4.

lleferring now to Figure a, the hydrodynamical pressure on the hull, when in motion, is'represented by the line 13, which indicates that from the two resultants 14 of the elementary pressures a totally axial resultant 15 is obtained which is directed from stern to bow. This resultant indicates that the resistance to moti'on'- of the hulfl through theA water atl the forward end of the' vessel is partly' compensated.

Further, account must be taken' of the' fact that the-reaction represented by the line 16' of the rudder'17 on the water has, with reference to the centre of gravity G of the hulli a lever arm 18 which is bigger than would be the lever arm 19 should the centre of gravity' be at a point G' situated midway between the stern and the stern as occurs in vessels' of' ordinary construction. It should alsol be ob'- served that the resultant 20 of the reactions of the water on the h-ull during movement has, with regard to the actual centre of: grav'- ity Gr, a lever arm 21 which is sma'l'lerl than would be the lever arm 20' of the resultant should the centre of gravity be at Gf.

Having now particularly descri'bed and2 ascertained' the nature of my said inventi'on' and in what. manner the same is to' be performed, I declare that what I claim is:

A hull, with the characteristics that the'v hull below the' water with' a maximum' wi'dth at about one-third' to= one-fifth of the length of vesselv includes waterlines from' the bow in the shape of a drop'anof changes at tlie'fore part into a Shapel above the' water which has the usual waterlines tapering towards the bow, the edge of the stem reaching below' the' surface of the water, bow" screws and' the stern screws, the latter being located as far as possible towards the l'ongitudnal center, and the upper structures seen in horizonta'l sectional view having a form of drop corre- 1 sponding to' the hull' below the water line.

In testimony whereof .afix my signature.

LUIGI GI-IIRARDI.

IGO 

